Unless otherwise indicated herein, the approaches described in this section are not prior art to the claims in this application and are not admitted to be prior art by inclusion in this section.
In the wideband RF telecommunication system, Multi-carrier signals used to be amplified simultaneously in one and the same power amplifier for cost reason.
FIG. 1 shows the block diagram of a feed-forward amplifier.
As shown in FIG. 1, an input signal is split into two branches, one for a non-linear amplifier to be amplified and the other for generating pure inter-modulation products.
In the first branch, the non-linear amplifier will amplify the input signal and produce the inter-modulation products. A small part of non-linear amplifier output with amplified input signal and inter-modulation products will be coupled and opposite phased. In the second branch, the input signal will be fed-forward to produce the opposite phased inter-modulation products (i.e., pure inter-modulation products) with the coupled non-linear amplifier's output signal. Next, a linear amplifier will amplify this opposite phased inter-modulation products into proper amplitude, and then add it to the non-linear amplifiers output to cancel the inter-modulation products. At last, an intentional output signal without inter-modulation products will be generated and output.
One problem in this solution is that actual output signal cannot be observed or checked, thus the quality of the actual output signal cannot be insured. Further, the opposite phased inter-modulation products are produced in analog domain thus cannot be dynamically adjusted in their amplitude, phase and delay in accordance with the real-time inter-modulation products of the non-linear amplifier output. As a result, it is impossible to dynamically optimize actual output signal to an ideal intentional signal.
Therefore, there is a need to develop a new feed-forward amplifier which can dynamically produce ideal phase-inverted inter-modulation products that have almost identical amplitude, calibrated delay and inversed phase in comparison with the inter-modulation products output from the non-linear amplifier, hence intentional output signal without any inter-modulation products can be generated and, meanwhile redundant non-linear amplifier will not be introduced.